Best Management Practices for Sustainable Crop Nutrition in Bulgaria

In 2008, a 5-year project was established in Bulgaria with the general goal of improving cultivation systems in Bulgaria’s agriculture through efficient and sustainable use of plant nutrients. About 50 researchers and discipline specialists are taking part in the project. Project activities include: 1) evaluation of soil nutrient status through summarization of past national soil surveys and more recent localized regional surveys; 2) systematic summarization of past relevant soil fertility research and identification of information gaps; 3) nutrient omission/addition plot trials on target crops; 4) development of tools for site-specific nutrient management that deliver updated recommendations to farmers and farmer advisers; and 5) outreach activities to assure appropriate use of the developed tools.

After conducting a soil test survey of pilot regions and creating a GIS database with soil and field data attributes in 2009 and 2010, layers were created with low, medium, and high content of P and K. The emphasis in 2011 was in the Northwest and Southwest parts of Bulgaria where additional soil sampling was conducted to better assess the soil fertility tendencies of these regions. In 2009, an Access database was structured for past soil fertility research and to accommodate new project data. In 2010, data obtained from long-term crop field experiments conducted after 1974 were entered into the database. The archive now consists of data from 87 experiments at 26 sites and 8 main soil types.

Four years of fertilizer omission/addition field plot trials (NPK or NPKMg as complete treatments) have now been completed. Crops tested were wheat, barley, maize, sunflower, oilseed rape, potatoes, tomatoes, pepper, apricots, peaches, chokeberry, and wine grapes. The average yield increase over four sites and four years from the NPK treatment compared to the no-fertilizer control for the five field crops was 56%. Average yield declines from omitting a nutrient from the NPK treatment for the field crops were 23%, 7%, and 8% for N, P and K, respectively. This was less response than expected for P and more response than expected for K based on the soil test levels of the study sites.

The project is in its recommendation development phase where data from the new field trials are being integrated with legacy data and soil resource considerations to create new recommended fertilizer BMPs for Bulgaria. These should be completed in 2014.